A rotation of a crankshaft in an internal combustion engine includes a rotation fluctuation of a constant size. An instantaneous rotation fluctuation of the crankshaft generates a slip of a belt due to an instantaneous driving load in an accessory pulley of an engine Front End Accessory Drive (FEAD) belt system or an accessory belt system.
A noise and an abrasion at the accessory belt is caused by such a slip of the pulley and the belt, and a span vibration of the FEAD belt is generated by an excitation force of a periodic ascending or descending in the length direction of the belt.
An alternator of the accessory belt system includes a rotor having a large inertial force and a small pulley. Accordingly, a driving load is generated that is larger than that of the other pulley by the instantaneous rotation fluctuation of the crankshaft.
Therefore the slip of the belt is largely generated in the pulley of the alternator. Accordingly, a pulley may be used that includes special functions such as an Over-running Alternator Pulley (OAP) and an Over-running Alternator Decoupler (OAD) to improve durability and a noise of the accessory belt.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.